1. Field of the Invention
The present invention relates to a sensor element and a gas sensor.
2. Description of the Related Art
There is so far known a gas sensor including a sensor element that detects the concentration of a specific gas, e.g., NOx, in measurement object gas, such as automobile exhaust gas. It is also known to form a protective layer on a surface of the sensor element in that type of gas sensor. For example, Patent Literatures (PTLs) 1 and 2 disclose that the protective layer is formed on the surface of the sensor element by printing or plasma spraying. According to the disclosures of PTLs 1 and 2, cracking, etc. of the sensor element attributable to adherence of moisture in the measurement object gas, for example, can be suppressed by forming the protective layer.